Data files for "Optimisation of dynamic nuclear polarisation using "off-the-shelf" Gd(III)-based polarising agents" NMR Nuclear Magnetic Resonance data, measured using a Bruker Avance 600 MHz DNP MAS NMR spectrometer at the University of Nottingham EPR Electron Paramagnetic Resonance data, measured using X-band and Q-band Bruker E580 Elexys spectrometers at the University of Manchester HRMS High-resolution Mass Spectrometry reports, measured using an Agilent 6540 Quadrupole-Time-of-Flight mass spectrometer at the University of Liverpool